12.  Simple Ideas, [word in Greek], and adequate.

Thus the mind has three sorts of abstract ideas or nominal essences: 

First, simple ideas, which are [word in Greek] or copies; but yet certainly adequate.  Because, being intended to express nothing but the power in things to produce in the mind such a sensation, that sensation, when it is produced, cannot but be the effect of that power.  So the paper I write on, having the power in the light (I speak according to the common notion of light) to produce in men the sensation which I call white, it cannot but be the effect of such a power in something without the mind; since the mind has not the power to produce any such idea in itself:  and being meant for nothing else but the effect of such a power that simple idea is [* words missing] the sensation of white, in my mind, being the effect of that power which is in the paper to produce it, is perfectly adequate to that power; or else that power would produce a different idea.

13.  Ideas of Substances are Echthypa, and inadequate.

Secondly, the complex ideas of substances are ectypes, copies too; but not perfect ones, not adequate:  which is very evident to the mind, in that it plainly perceives, that whatever collection of simple ideas it makes of any substance that exists, it cannot be sure that it exactly answers all that are in that substance.  Since, not having tried all the operations of all other substances upon it, and found all the alterations it would receive from, or cause in, other substances, it cannot have an exact adequate collection of all its active and passive capacities; and so not have an adequate complex idea of the powers of any substance existing, and its relations; which is that sort of complex idea of substances we have.  And, after all, if we would have, and actually had, in our complex idea, an exact collection of all the secondary qualities or powers of any substance, we should not yet thereby have an idea of the essence of that thing.  For, since the powers or qualities that are observable by us are not the real essence of that substance, but depend on it, and flow from it, any collection whatsoever of these qualities cannot be the real essence of that thing.  Whereby it is plain, that our ideas of substances are not adequate; are not what the mind intends them to be.  Besides, a man has no idea of substance in general, nor knows what substance is in itself.

14.  Ideas of Modes and Relations are Archetypes, and cannot be adequate.

Thirdly, complex ideas of modes and relations are originals, and archetypes; are not copies, nor made after the pattern of any real existence, to which the mind intends them to be conformable, and exactly to answer.  These being such collections of simple ideas that the mind itself puts together, and such collections that each of them contains in it precisely all that the mind intends that it should, they are archetypes and essences of modes that may exist; and so are designed only for, and beling only to such modes as, when they do exist, have an exact conformity with those complex ideas The ideas, therefore, of modes and relations cannot but be adequate.